Many vehicles are used over a wide range of vehicle speeds, including both forward and reverse movement. Some types of engines, however, are capable of operating efficiently only within a narrow range of speeds. Consequently, transmissions capable of efficiently transmitting power at a variety of speed ratios are frequently employed. When the vehicle is at low speed, the transmission is usually operated at a high speed ratio such that it multiplies the engine torque for improved acceleration. At high vehicle speed, operating the transmission at a low speed ratio permits an engine speed associated with quiet, fuel efficient cruising.
FIG. 1 depicts a typical front wheel drive transaxle 10. Flow of mechanical power is shown by solid lines. Power is provided by internal combustion engine 12. The crankshaft of engine 12 drives torque converter 14. Torque converter 14 permits the engine to idle while the vehicle is stationary. Torque converter 14 transmits the power to gearbox 16. In some operating conditions, torque converter 14 may decrease shaft speed and increase shaft torque. Gearbox 14 adjusts the speed and torque according to current vehicle requirements. Engine 12, torque converter 14, and gearbox 16 are situated on a common axis offset from the axis about which the front wheels 18 and 20 rotate. Transaxle 10 includes axis transfer components 22 to transfer power from gearbox 16 to differential 24, which is located approximately on the wheel rotation axis. These components may also multiply the torque by a final drive ratio. Differential 24 transmits the power to left and right wheels 18 and 20 while permitting slight speed differences when the vehicle turns a corner.